Metal oxide composite cathode material for high energy density batteries

ABSTRACT

An electrochemical cell incorporating cathode materials comprising at least one metal oxide, at least one metal, or mixture of metals or metal oxides incorporated in the matrix of a host metal oxide. The cathode materials of this invention are constructed by the chemical addition, reaction, or otherwise intimate contact of various metal oxides and/or metal elements during thermal treatment in mixed states. The materials thereby produced contain metals and oxides of the groups IB, IIB, IIIB, IVB, VB, VIB, VIIB, and VIII, which includes the noble metals and/or their oxide compounds. 
     The incorporation of the metal oxides, metals or mixtures thereof substantially increases the discharge capacity and the overall performance of the cathode materials.

BACKGROUND OF THE INVENTION

This invention relates to the art of electrochemical cells and moreparticularly to a new and improved electrochemical cell and cathodetherefor comprising a Group IA metal anode and a composite metal/metaloxide or metal oxide cathode.

Light metals have exceptionally high energy density when employed as theanode material in electrochemical cells owing to their low atomic weightand high standard potential. This high chemical activity of light metalanode material requires the use of a nonaqueous electrolyte and acathode which meets the rigorous requirements for such a cell. Mostcathode materials are too readily soluble in a nonaqueous electrolyte,and thereby reduce the useful capacity of such an electrode afterstorage.

It is known to use metal oxides, particularly heavy metal oxides, ascathode materials in nonaqueous electrochemical cells. For example U.S.Pat. No. 3,945,848 discloses the use of cobalt (III) oxide, U.S. Pat.No. 4,158,722 discloses a cell employing a chromium oxide cathode, andU.S. Pat. No. 3,423,242 discloses a cell employing a vanadium pentoxidecathode.

A continuing problem encountered with these and other cells having metaloxide cathodes is the relatively low discharge potential and consequentlow energy density. Additionally, as noted above, the appreciablesolubility of the metal oxides in the nonaqueous electrolyte leads to ametal deposit on the anode after extended storage, thereby causing aloss of capacity.

SUMMARY OF THE INVENTION

This invention relates to electrochemical cells comprised of a Group IAmetal acting as the anode and a cathode of a composite material preparedby the chemical addition, reaction, or otherwise intimate contact ofseveral metal oxides, metal or metal oxide/elemental metal combinationsduring thermal treatment in mixed states. Alternatively, the cathode maycomprise the product of a single metal oxide thermally treated accordingto the invention.

It is an object of this invention to provide a new and improvedelectrochemical cell having relatively high energy density, dischargecapacity, and a wide operating temperature range.

It is a further object of this invention to provide such anelectrochemical cell of high reliability and utility even afterprolonged storage.

It is another object of this invention to provide such anelectrochemical cell having a relatively high open circuit voltage andcurrent capacity.

It is still another object of this invention to provide anelectrochemical cell having an oxidizable active anode material and acathode material combining various metal oxides or oxide/elemental metalcombinations, particularly metal oxides or oxide/elemental metalcombinations prepared by the thermal treatment methods of the invention.

The foregoing and additional advantages and characterizing features ofthe present invention will become apparent from the following detaileddescription which includes the following figures:

FIG. 1 is a voltage-time plot for a cell according to one embodiment ofthe invention;

FIG. 2 is a voltage-cumulative capacity plot for a cell according to oneembodiment of the invention;

FIG. 3 is a voltage-time plot for a cell according to another embodimentof the invention.

DETAILED DESCRIPTION OF THE INVENTION

The electrochemical cell of the present invention comprises an anode ofa metal selected from Group IA of the Periodic Table of the Elements,including lithium, sodium, potassium, etc., and their alloys andintermetallic compounds including, for example Li-Si, Li-Al, Li-B andLi-Si-B alloys and intermetallic compounds. The form of the anode mayvary, but typically is a thin sheet or foil of the anode metal, and acurrent collector having an extended tab or lead affixed to the anodesheet or foil.

The electrochemical cell of the present invention further comprises acathode of electronically conductive composite material which serves asthe other electrode of the cell. The electrochemical reaction at thecathode involves conversion of ions which migrate from the anode to thecathode into atomic or molecular forms. The composite cathode materialof the invention comprises at least one metal oxide, at least one metal,or a mixture of metals or metal oxides incorporated in the matrix of ahost metal oxide.

The cathode material of this invention can be constructed by thechemical addition, reaction, or otherwise intimate contact of variousmetal oxides and/or metal elements during thermal treatment in mixedstates. Alternatively, the cathode material may be the product of thethermal treatment of a single metal oxide. The materials therebyproduced contain metals and oxides of the groups IB, IIB, IIIB, IVB, VB,VIB, VIIB, and VIII which includes the noble metals and/or their oxidecompounds.

According to the invention, readily decomposable compounds consisting ofmetals from Groups IB, IIB, IIIB, IVB, VB, VIB and VIIB, as well assimilarly decomposable compounds from Group VIII, are thermally treatedso as to effect the rapid preparation of the oxides or the respectivemetal elements themselves to be utilized further in the preparation ofsuitable cathode materials. Such readily decomposable materials include,but are not limited to, those classes of compounds known as nitrates,nitrites, carbonates, and/or ammonium salts. The precursor materials(i.e., nitrates, nitrites, carbonates, ammonium compounds, etc.) may bedecomposed in a combined state or individually decomposed and thereaftercombined in an oxide/decomposable metal salt compound and subsequentlydecomposed to form the cathode composite matrix. Such compositematerials may be pressed into a cathode pellet with the aid of asuitable binder material and a material having electronic conductioncharacteristics such as graphite. In some cases, no binder material orelectronic conductor material is required to provide a similarlysuitable cathode body. Further, some of the cathode matrix samples mayalso be prepared by rolling, spreading or pressing a mixture of thematerials mentioned above onto a suitable current collector such asExmet wire mesh. The prepared cathode bodies as described above may beused as either a solid cathode prepared by directly pressing thematerial into a battery can assembly or a wound cathode structuresimilar to a "jellyroll". The cathode is separated in both cases fromthe Group IA anode material by a suitable separator material such as aporous glass woven or Teflon (Dupont) fabrics.

Preferred cathode composites are prepared by thermally decomposing avanadium salt, suitably ammonium metavanadate, to produce vanadiumpentoxide. A decomposable metal salt, suitably the nitrate, of a secondmetal is then added to the vanadium pentoxide, thoroughly mixedtherewith and thereafter ignited. The second metal is most preferablyselected from the group consisting of silver, copper, manganese andmixtures thereof. The resultant composite cathode includes V₂ O_(x)wherein x≦5 combined with one or more of Ag₂ O_(x) wherein x=0 to 1;CuO_(x) wherein x=0 to 1; and M_(n) O_(x) wherein x=1 to 3. Thus, thecomposite cathode material may be described as a metal oxide-metaloxide, a metal-metal oxide, or a metal-metal oxide-metal oxide.

The electrochemical cell of the present invention further comprises anonaqueous, ionic conductive electrolytic solution of a Group IA metalsalt operatively associated with the anode and the cathode. Theelectrolytic solution serves as a medium for migration of ions betweenthe anode and cathode during the cell electrochemical reactions. Thenonaqueous solvents suitable for the invention are chosen so as toexhibit those physical properties necessary for ionic transport (lowviscosity, low surface tension, and wettability). The nonaqueous solventof the electrolyte may be any one or more of the organic solvents whichis substantially inert to the anode and cathode electrode materials,such as tetrahydrofuran, propylene carbonate, methyl acetate,acetonitrile, dimethyl sulfoxide, dimethyl formamide, dimethylacetamide, 1,2-dimethoxyethane and others. The nonaqueous solvent alsomay be one or a mixture of more than one of the inorganic solvents whichcan serve as both a solvent and a depolarizer, such as thionyl chloride,sulfuryl chloride, selenium oxychloride, chromyl chloride, phosphorylchloride, phosphorous sulfur trichloride and others. The Group IA metalsalt of the nonaqueous electrolytic solution may be chosen from, forexample, lithium halides, such as LiCl and LiBr, and lithium salts ofthe LiMX_(n) type, such as LiAlCl₄, Li₂ Al₂ Cl₆ O, LiClO₄, LiAsF₆,LiSbF₆, LiSbCl₆, Li₂ TiCl₆, Li₂ SeCl₆, Li₂ B₁₀ Cl₁₀, Li₂ B₁₂ Cl₁₂ andothers. Alternatively, the corresponding sodium or potassium salts maybe used.

When the mechanical structure or configuration of the cell requires, aseparator can be employed to provide physical separation between theanode and the cathode current collectors. The separator is ofelectrically insulative material to prevent an internal electrical shortcircuit in the cell between the anode and the cathode currentcollectors. The separator material also must be chemically unreactivewith the materials of the anode and cathode current collectors and bothchemically unreactive with and insoluble in the electrolytic solution.In addition, the separator material must have a degree of porositysufficient to allow flow therethrough of the electrolytic solutionduring the electrochemical reaction of the cell. Illustrative separatormaterials include non-woven glass, Teflon, glass fiber material,ceramics and materials commercially available under the designationsZitex (Chemplast Inc.), Celgard (Celanese Plastic Company Inc.) andDexiglas (C. H. Dexter, Div. Dexter Corp.). The form of the separatortypically is a sheet which is placed between the anode and cathode ofthe cell in a manner preventing physical contact between the anode andcathode, and such contact also is prevented when the combination isrolled or otherwise formed into a cylindrical configuration.

The electrochemical cell of the present invention operates in thefollowing manner. When the ionic conductive electrolytic solutionbecomes operatively associated with the anode and cathode of the cell,an electrical potential difference is developed between terminalsoperatively connected to the anode and cathode. The electrochemicalreaction at the anode includes oxidation to form metal ions duringdischarge of the cell. The electrochemical reaction at the cathodeinvolves conversion of ions which migrate from the anode to the cathodeinto atomic or molecular forms. It is observed that the systems of thisinvention have a wide operating temperature range, e.g., -55° to +225°C.

The electrochemical cell according to the present invention isillustrated further by the following examples.

EXAMPLE I

Commercially available ammonium vanadate, NH₄ VO₃ (Cerac, 99.99%,-80mesh) was thermally decomposed to vanadium pentoxide, V₂ O₅, in an airfurnace at elevated temperatures. Evidence for the completedecomposition was based upon the distinct lack of NH₃(g) and thecomparison of product yield to the theoretical yield for V₂ O₅.

Aliquots of aqueous AgNO₃ of known concentration were quantitativelyadded to weighed amounts of the previously prepared V₂ O₅. The mixturewas stirred and evaporated to dryness in an air oven maintained at atemperature less than 100° C. At the end of the initial drying period,the mixtures were stirred and ground to ensure homogeneity. After aperiod of time, the samples were subsequently baked out at an initialtemperature of about 180° C. Upon reaching thermal equilibrium, the oventemperature level was gradually raised to about 360° C. and maintainedat that temperature for a minimum period of 24 hours. During the finalheating/decomposition period, copious amounts of nitrogen oxide gaseswere detected. At specific time intervals after the evolution of thenitrogen oxides, the samples were removed and stirred vigorously.Finally, each sample was removed from the furnace, cooled in adesiccator, and reweighed.

Various weighed amounts of the treated material were blended with theappropriate amounts of graphite powder (Fisher) and Teflon 7A binder(Dupont) and intimately mixed. A one-inch diameter disc of the cathodematerial was then pressed onto a nickel Exmet (Delker Corp.) currentcollector. The construction of the remainder of the cell is effected byemploying the following steps:

Separator material (Mead glass, 6.5% binder) was cut to the appropriatedimensions and wrapped around the cathode body. A piece of lithium metalpartially supported by a nickel Exmet screen and lead was fashioned tosurround the cathode. The cell was then fitted into the appropriatecontainer. An exact amount of the electrolyte solution comprised of onemolar lithium perchlorate (LiClO₄) in an equal volume mixture ofpropylene carbonate and 1,2-dimethoxyethane was added to each of thecells.

Specifically, 1.82 grams of silver vanadium oxide (the silver tovanadium ratio equals 0.31) was weighed and mixed with 0.3 g graphitepowder and 0.3 g Teflon 7A solid binder. This cathode material waspressed into a disc at a 20,000 lb. load. The remainder of the cell wasconstructed as previously described. The open circuit voltageimmediately after cell construction was 3.93 volts. A load of 1.5 kohmswas applied to the cell. The voltage-time results are illustrated inFIG. 1. A plot of voltage versus cumulative capacity is given in FIG. 2.It is apparent that the discharge curve for this particular system isnearly linear.

EXAMPLE 2

Samples of copper vanadium oxide were prepared in the same manner asdescribed in Example 1. Various amounts of the thus treated materialwere mixed with the appropriate amounts of graphite powder and bindermaterial. The construction of the remainder of the cell correspondsdirectly to that for Example 1.

Specifically 2.3 g of copper vanadium oxide (the copper to vanadiumratio equals 0.35) was intimately mixed with 0.3 g of Teflon 7A binderand 0.3 g of carbon graphite. This cathode mixture was pressed into aone inch disc at a 20,000 lb. load pressure. The remainder of the cellwas constructed as previously described. The open circuit voltageimmediately following cell construction was 3.64 volts. A load of 1.5kohms was applied to the cell. The cumulative capacity, to a 2 voltcutoff point, was 640 mAh. The voltage-time results are presented inFIG. 3.

EXAMPLE 3

Samples of copper vanadium oxide were prepared exactly as in Example 2.The one distinguishing alteration in cell construction was the use of 1MLiClO₄ in propylene carbonate alone. Significantly higher voltages underload were observed for this embodiment until a voltage of 3 volts wasreached. At that point, the values decreased to the 2 volt cutoffrapidly. The cumulative capacity was 150 mAh.

EXAMPLE 4

A cell consisting solely of V₂ O₅ from the decomposition of ammoniumvanadate as described in Example 1 was constructed. Specifically, 1.82 gof V₂ O₅, 0.3 g graphite, and 0.3 g of Teflon 7A was mixed and pressedinto the cathode structure as previously described in Examples 1-3. Theopen circuit voltage for this cell was 3.81 volts. A load of 1.5 kohmwas applied to the cell. A total of 8.5 mAh was obtained for thecapacity of this cell to a 2 volt cutoff value.

EXAMPLE 5

Commercially available silver oxide, Ag₂ O (Cerac, 99.5%), was thermallytreated at 145° C. in an air oven. Cells were then constructed in theexact manner as previously described. Specifically 2.2 g of Ag₂ O wasintimately mixed with 0.46 g of Teflon 7A and 0.43 g of graphite. Theelectrolyte for this cell was 1M LiClO₄ in propylene carbonate only. Theopen circuit voltage immediately after cell construction was 3.56 volts.A load of 1.5 kohm was applied to the cell and, after a period of fourhours, the running voltage dropped to 2.4 volts. The total capacity tothe 2 volt cutoff, however, was 341 mAh.

EXAMPLE 6

Silver oxide, Ag₂ O, was treated in the manner as described in Example5. Specifically, 2.1 g of Ag₂ O was intimately mixed with 0.44 g Teflon7A binder and 0.41 g of graphite powder. The cell thereby produceddiffered from that in Example 5 by the electrolyte solution--1M LiClO₄in 50/50 (V/V) propylene carbonate/1,2-dimethoxyethane. The open circuitvoltage after cell preparation was 3.54 volts. A load of 1.5 kohm wasapplied to the cell. As with the case of Example 5, the running voltagedecreased rapidly to 2.4 volts, (8.5 h). The cumulative capacity,however, to the 2 volt cutoff, was 441 mAh.

EXAMPLE 7

X-ray powder patterns have been obtained for V₂ O₅, silver vanadiumoxide with a silver to vanadium ratio of 0.35, silver vanadium oxidewith a silver to vanadium ratio of 0.50, and copper vanadium oxide witha copper to vanadium ratio of 0.35. The results are numericallypresented in Table I. It can be readily seen that the precursormaterial, V₂ O₅, has been significantly altered in all three otherexamples so as to produce new chemical species. The above is especiallytrue for the silver vanadium oxide with a silver to vanadium ratio of0.35 and silver vanadium oxide with a silver to vanadium ratio of 0.50where there is strong definite proof that the symmetries tocorresponding lattice d-spacings for 20 values above 60° C. have beendestroyed, thereby indicating the likely inclusion of silver species orcopper species between those planes.

                  TABLE I                                                         ______________________________________                                        X-ray Powder Pattern Data for V.sub.2 O.sub.5 and                             Metal Composite Cathode Materials                                             2θValue                                                                         Ag.sub. 0.035 VO.sub.x                                                                     Ag.sub.0.50 VO.sub.x                                                                    Cu.sub.0.35 VO.sub.x                           V.sub.2 O.sub.5                                                                       (x = 2.5)    (x = 2.5) (x = 2.5)                                      ______________________________________                                        19.3    22.4                   24.2                                           25.2    25.5                   25.6                                           30.0    28.9         28.8      28.6                                                   29.5         30.1      30.5                                           31.4                 31.8                                                     33.3    33.3         35.7                                                             34.7                                                                  38.1    38.1         38.1      38.1                                           40.3                 40.1                                                     44.3    44.3         44.2      44.3                                           46.4    45.7                                                                  47.8    48.6                                                                  50.25   50.3         50.5      50.7                                           51.2    52.6                                                                  54.75   59.3         53.4      56.6                                           60.2    60.6         59.5      60.6                                           61.2                 62.25                                                    64.7                           64.6                                           71.6                                                                          77.7                           77.7                                           ______________________________________                                    

EXAMPLE 8

A test cell was constructed having a lithium anode, a composite cathodematerial as prepared in Example I and an electrolyte comprising lithiumbromide dissolved in selenium oxychloride. In particular, the anode ofthe cell was a lithium foil having a width of about 1.4 cm, a length ofabout 6.6 cm. and a thickness of about 0.06 cm. with a nickel currentcollector having an extending lead or tab cold welded on the lithiumfoil. The cathode was fabricated by providing a thin layer of thecomposite cathode material having a width of about 1.5 cm, a length ofabout 7 cm. and a weight of about 0.17 g and then by pressing this layeron a thin expanded metal screen of stainless steel having an extendinglead or tab. A separator in the form of a sheet of Celgard material alsowas provided and placed between the anode and cathode layers, whereuponthe anode/separator/cathode assembly or combination was rolled or woundinto a cylindrical configuration and placed in a glass vial having anouter diameter of about 1.3 cm. with the anode and cathode currentcollector leads extending out through the open end of the vial. Adepolarizer-electrolyte solution was prepared comprising lithium bromidedissolved in selenium oxychloride to provide a 0.1 M solution having atotal volume of 2.0 ml. The solution was injected into the glass vial,and then the open end of the vial was sealed closed with a Teflon linedstopper in a manner maintaining the spaced anode and cathode leadsexternally accessible for electrical connection. The test cell had anopen circuit voltage of about 3.5 volts and then an initial load voltageof about 3.4 volts when discharged at room temperature under a constantload of 3.3 kilohms.

EXAMPLE 9

A test cell was constructed having a lithium anode, a composite cathodematerial as prepared in Example 2 and an electrolyte comprising lithiumaluminum tetrachloride dissolved in thionyl chloride. In particular, theanode of the cell was a lithium foil having a width of about 1.5 cm., alength of about 7 cm and a thickness of about 0.06 cm. with a nickelcurrent collector having an extending lead or tab cold welded on thelithium foil. The cathode was fabricated by providing a quantity ofcarbon having a weight of about 0.25 g and containing binder of Teflonmaterial in an amount of approximately 5% by weight and spreading thecarbon onto a nickel expanded metal element having a width of about 1.5cm. and a length of about 7 cm. and including an extending lead or tab.A separator in the form of a sheet of nonwoven glass material wasprovided and placed between the anode and cathode layers. Theanode/separator/cathode assembly or combination was wound into acylindrical shape and inserted in a glass vial having an outer diameterof 1.3 cm. with the anode and cathode current collector leads extendingout through the open end of the vial. The electrolyte solution wasprepared comprising lithium aluminum tetrachloride dissolved in thionylchloride to provide a 1.0 M solution having a total volume of 2 ml. Thesolution was injected into the glass vial, and then the open end of thevial was sealed closed with a Teflon lined stopper in a mannermaintaining the spaced anode and cathode leads externally accessible forelectrical connection. The test cell had an open circuit voltage of 3.6volts and was discharged at room temperature under a constant load of182 ohms with the average current drain rate being approximately 20milliamperes. During discharge the cell had an initial load voltage ofabout 3.4 volts and a load voltage of about 3.3 volts after a 32 hourdischarge period.

The above detailed description and examples are intended for purposes ofillustrating the invention and are not to be construed as limiting.

What is claimed is:
 1. An electrochemical cell having an anode of aGroup 1A metal which is electrochemically oxidizable to form metal ionsin the cell upon discharge to generate electron flow in an externalelectrical circuit connected to the cell and a cathode of electronicallyconductive material and characterized by an ionic conductive electrolytesolution operatively associated with the anode and the cathode, thecathode comprising a composite oxide matrix of vanadium oxide chemicallyreacted with at least one other metal selected from the group consistingof groups IB, IIB, IIIB, IVB, VIB, VIIB and VIII, said composite oxidebeing the thermal decomposition and reaction product of a mixture ofvanadium oxide with at least one decomposable metal compound of saidgroups.
 2. An electrochemical cell of claim 1, wherein the decomposablecompound is selected from the group consisting of metal nitrate, metalnitrite, metal carbonate, and ammonium salts of transition metaloxyanions.
 3. An electrochemical cell of claim 1 wherein one componentof the cathode comprises V₂ O_(x) wherein x is less than or equal to 5prepared by the thermal treatment of ammonium vanadate.
 4. Anelectrochemical cell of claim 1 wheren one component of the cathodecomprises Ag₂ O_(x) wherein x ranges from 0 to 1 prepared by the thermaltreatment of silver nitrate.
 5. An electrochemical cell of claim 1,wherein the cathode comprises a mixture of V₂ O_(x) wherein x is lessthan or equal to 5 and Ag₂ O_(x) wherein x ranges from 0 to 1 preparedby the thermal treatment of vanadium pentoxide and silver nitrate.
 6. Anelectrochemical cell of claim 1, wherein the cathode further comprises asuitable binder material.
 7. An electrochemical cell of claim 6, whereinthe binder material is carbon.
 8. An electrochemical cell of claim 6,wherein the binder material is a mixture of carbon and Teflon.
 9. Anelectrochemical cell of claim 1, wherein the electolytic solutioncomprises a Group IA metal salt dissolved in a nonaqueous solvent. 10.An electrochemical cell of claim 9, wherein the nonaqueous solventcomprises an inorganic solvent.
 11. An electrochemical cell of claim 10,wherein the nonaqueous solvent comprises an organic solvent.
 12. Anelectrochemical cell of claim 1, wherein the cathode comprises a mixtureof silver vanadium oxide and manganese oxide MnO_(x) wherein x rangesfrom 1 to
 3. 13. An electrochemical cell of claim 1, wherein the cathodecomprises a mixture of Ag₂ O_(x) wherein x ranges from 0 to 1 andmanganese oxide MnO_(x), wherein x ranges from 1 to 3 prepared by thesimultaneous decomposition of silver nitrate and manganese nitrate. 14.An electrochemical cell of claim 1, wherein the cathode comprisesmanganese oxide MnO_(x) wherein x ranges from 1 to 3 prepared by thedecomposition of manganese nitrate with subsequent addition of Ag₂ O_(x)wherein x ranges from 0 to
 1. 15. An electrochemical cell of claim 1,wherein the cathode comprises a mixture of silver oxide, Ag₂ O_(x)wherein x ranges from 0 to 1 and manganese oxide, MnO_(x) wherein xranges from 1 to 3 prepared by the decomposition of silver nitrate inthe presence of manganese oxide.
 16. An electrochemical cell of claim 1,wherein one component of the cathode comprises copper vanadium oxide.17. An electrochemical cell of claim 1, wherein the cathode comprises amixture of copper vanadium oxide and manganese oxide, MnO_(x) wherein xranges from 1 to
 3. 18. An electrochemical cell of claim 1, wherein onecomponent of the cathode comprises a mixture of copper oxide, CuO_(x),wherein x ranges from 0 to 1 and manganese oxide, MnO_(x), wherein xranges from 1 to
 3. 19. A cathode for an electrochemical cell comprisingthe composite oxide matrix of vanadium oxide chemically reacted with atleast one metal selected from the group consisting of silver, copper,manganese and mixtures thereof, said composite oxide being the thermaldecomposition and reaction product of a mixture of vanadium oxide withat least one decomposable metal compound of said group.
 20. A cathode ofclaim 19, wherein the decomposable compound is selected from the groupconsisting of metal nitrate, metal nitrite, metal carbonate, andammonium salts of transition metal oxyanions.
 21. A cathode of claim 19,wherein one component of the cathode comprises V₂ O_(x) wherein x isless than or equal to 5 prepared by thermal treatment of ammoniumvanadate.
 22. A cathode of claim 19, wherein one component of thecathode comprises Ag₂ O_(x) wherein x ranges from 0 to 1 prepared bythermal treatment of silver nitrate.
 23. A cathode of claim 19, whereinthe cathode comprises a mixture of V₂ O_(x) wherein x is less than orequal to 5 and Ag₂ O_(x) wherein x ranges from 0 to 1 prepared bythermal treatment of a mixture of vanadium pentoxide and silver nitrate.24. A cathode of claim 19, wherein the cathode further comprises asuitable binder material.
 25. A cathode of claim 24, wherein the bindermaterial is carbon.
 26. A cathode of claim 24, wherein the bindermaterial is a mixture of carbon and Teflon.
 27. The cathode of claim 19wherein the decomposable metal compound is a copper salt and whereinsaid thermally decomposed product includes CuO_(x) wherein x ranges from0 to
 1. 28. The cathode of claim 19 wherein the decomposable metalcompound is a manganese salt and wherein said thermally decomposedproduct includes M_(n) O_(x) wherein x ranges from 1 to
 3. 29. Thecathode of claim 19 wherein the decomposable metal compound comprises amixture of copper and manganese salts and wherein said thermallydecomposed product includes CuO_(x) wherein x ranges from 0 to 1 andMnO_(x) where x ranges from 1 to
 3. 30. The cathode of claim 19 whereinthe decomposable metal compound comprises a mixture of silver andmanganese salts and wherein said thermally decomposed product includesAg₂ O_(x) wherein x ranges from 0 to 1 and MnO_(x) wherein x ranges from1 to 3.